Motorists travelling between Derry and Letterkenny - in both directions - are being advised to allow extra time for their journey.
A garda checkpoint is in operation on the Letterkenny side of Newtowncunningham.
This has resulted in a considerable slow down in traffic with a consequential knock-on effect in terms of journey times.
Meanwhile, traffic congestion is beginning to worsen on the N56 beside Letterkenny University Hospital on the main road from Letterkenny to Dunfanaghy.
A stop-go operation is in place, due to construction work for Irish Water which involves pipe-laying.
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